Ok so friday I fitted the Hytech and the difference in noticeable.
At low rpm it is quieter and more responsive than the J's, going up through to vtec it's so much smoother!!! Power feels slightly more throughout the rev range even up at 8000rpm where the 4-1 "should" be better suited.
So now I'm running Hytech 4-2-1, 63mm flexi-hose and 63mm pipe to centre box, then 60.5mm through to 5zigen backbox with a tiny resonator just before the backbox.
I have not dyno'd the car yet, but had another race with a mate in his stock JDM ITR for real life comparison:
1st time we ran I had the J's Racing 4-1 and 57mm pipe to centre box, then 60.5 through to back, "previous owner cocked-up with decat". ITR would pull me immediately from a 3rd gear rolling start, 4th gear he ran away like 100meters ahead through to limiter.
This time, now with Hytech 4-2-1 & 63mm to 1st box, 3rd gear we next to each other with him gradually pulling only 1 car length, 4th he still pulls but ALOT less than before. Each run seemed like about 20meters.
^^^Bad way of explaining things I KNOW but I have no dyno curve as yet.
Next step is either Spoon drop in filter with stock box or J's Racing type Carbon intake... Suggestions?